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Molecular Basis of CNS Stimulation:

Molecular Basis of CNS Stimulation Imbalance between inhibitory and excitatory processes as in the brain. This hyper-excitability of neurons results from: potentiation or enhancement of excitatory neurotransmission(e.g. amphetamine) depression or antagonism of inhibitory transmission (e.g. Strychnine) presynaptic control of neurotransmitter release (e.g. picrotoxin)

Classification of CNS Stimulants:

Analeptic Stimulants:

Analeptic Stimulants diverse chemical class of agents majority can be absorbed orally have a short duration of action - primary expression of pharmacological effect is convulsions (tonic-clonic) uncoordinated pharmacological effect is terminated through hepatic metabolism Possible Common Mechanism of Action -ability to alter movement of chloride ions across neuronal membranes Therapeutic Uses Group as a whole has limited therapeutic use.

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Doxapram and Nikithamide - used to counteract postanesthetic respiratory depression and for acute hypercapnia in chronic pulmonary disease. Pentylenetetrazole - used clinically as a tool for screening latent epileptics and experimentally to screen compounds for anti-epileptic activity. Picrotoxin - used to study CNS mechanisms; it interferes with pathways that are strychnine resistant.

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Strychnine is a source of accidental poisoning. Also used to study CNS mechanism because of its relatively specific action as a glycine antagonist. Adverse Reactions: Convulsion is characterized by opisthotonos , i.e., tonic extension of body and all limbs. Back is arched and only the back of the head and the heels are touching the touching the surface. All sensory stimuli produce exaggerated response and slight sensory stimulation may trigger convulsion.

Treatment of Strychnine Poisoning:

Treatment of Strychnine Poisoning (1) Remove/reduce external sensory stimuli (2) Diazepam or Clonazepam I.V. or nitrous oxide by inhalation to depress CNS and stop convulsions which can be fatal

PSYCHOMOTOR STIMULANTS:

CHARACTERISTICS:

CHARACTERISTICS all compounds are absorbed well orally large portion of untransformed amphetamine is excreted unchanged in the urine. Consequently, acidifying the urine with ammonium chloride hastens its clearance, and thus reduces its reabsorption in the renal tubules. Overdose: hyperreflexia, tremors and convulsions Fatalities: hyperthermia rather than cardiovascular effects

Pharmacological Actions:

Pharmacological Actions The primary effects of an oral dose are wakefulness, alertness, decrease fatigue; mood elevation, increased ability to concentrate; an increase in motor and speech activity. Amphetamines also diminish the awareness of fatigue; person may push exertion to the point of severe damage or even death.

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Stimulate the respiratory center, especially when respiration is depressed by centrally acting drugs, (barbiturates and alcohol). Amphetamine can reverse the marked sedation and behavioral retardation resulting from reserpine-like drug. Depresses appetite by their action on the lateral hypothalamus rather than an effect on metabolic rate.

Mechanisms of Action:

Mechanisms of Action Releases monoamines at synapses in the brain and spinal cord. Inhibits neuronal uptake of monoamine Direct agonist of DA and 5-HT receptors Antagonist at certain adrenreceptors May inhibit monoamine oxidase.

Mechanisms of Action:

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Caffeine, the most widely used drug in the world, is a stimulant. Commonly found in coffee, tea, soft drinks, chocolate and a wide variety of over-the-counter medications, it is legal to buy and easily accessible. Caffeine is a physically addictive drug